06-16-2018, 03:34 PM
WF Lifetime Member
WF Supporting Member
Join Date: Jan 2014
Location: SouthEast of Denver
There isn't a lot that you can do to get any more power out of a 258/4.2.
These are low RPM, torquemonsters. You might be able to still find an aftermarket cam or a HO 4.0 cam might work. I'm (slowly) building a 258 that I bought as a core. Besides the .040 bore and a head that's planed just enough to flatten it out I'm going to stay stock.
Folks usually cam an engine to get more RPM out of it. That really doesn't work for the type of driving/wheeling that I do. When building something like an engine and varying from stock, beware of the rule of unintended consequences. IE... A 4.0 HO cam is intended for a FI engine that's timed by the computer. It may or not work well or it might work well with other modifications to the intake/exhaust systems.
You might find an old Edelbrock 4BBL intake manifold that usually comes with a reducer to allow for a 2BBL carb, but why?
Some guys use a 4.2 crank in a 4.0 block but since you already have your block at the machine shop, that probably isn't going to be practical for you.
I'm running a carb because that's what I want.
I think the best overall setup is a Howell FI setup with a HEI distributor.
You state that your use of the Jeep will be some trails and running around back roads.
4:10 gears will give you the biggest bang for your buck for that type of Jeeping.
I'm sure other posters have different opinions. The above is simply mine.
Keep us posted on your progress.
I could type several more paragraphs but that's the meat of it. Don't be shy about asking more questions.
Good Luck, L.M.
"Wrangler....It's not just a vehicle, It's a lifestyle".
1987 YJ-4.2L-Standard Shift- Re-manufactured Carter Carb-2" body Lift-31X10.5X15 BFG KOs-190K Miles No back seat.
HEI distributor with computer and all related relays and wiring removed.
12K Badlands winch with dual batteries.
Warn front bumper. Matching imitation Warn bumper on the rear.